The invention relates to a method of bonding two bodies using an adhesive, in which adhesive is applied between the two bodies which are then positioned relative to one another, after which the adhesive is made to cure.
The invention also relates to a composite body comprising at least two parts, at least two parts of which are bonded by means of an adhesive bond.
A method of bonding two bodies, one body being an optical component such as a mirror or lens, and the other body being a mount, is described in European Patent Specification EP 0090218. The mount is provided with a bore in which the optical component is fitted, a slot being formed between the inner wall of the mount and the outer wall of the optical component. This slot is completely or partly filled with adhesive.
Such optical assemblies are used, for example, in optical disc players. In these devices it is important that the optical parts are properly positioned relative to each other. Important in this connection is the positioning accuracy in the direction of the optical axis (Z-direction) of the optical assembly, in the directions of two axes (X- and Y-direction) extending perpendicularly to the optical axis and to one another, and in the directions of rotation about the latter axes.
The well-known method has the disadvantage that the curing of the adhesive between the optical component and the mount may bring about relatively large displacements of the optical component in the Z-direction due to the inevitable shrinkage of the adhesive layer during curing. Moreover, due to the occurrence of shrinkage stresses in the layer of adhesive there is a considerable chance that the optical component will tilt about the axes extending in the X- and Y-direction. In general, chemically-hardening adhesives comprising no or little solvent are used to cement such optical components to each other, which adhesives are based on a polymerization reaction of reactive monomers or oligomers. During this polymerization or curing reaction, which can be induced by light or heat, a volume reduction of the adhesive layer occurs which leads to shrinkage and shrinkage stresses in the adhesive layer. In order to manufacture accurate optical assemblies, so far, mechanical measures have been proposed, as described in U.S. Pat. No. 4,750,826, in which one of the walls to be cemented comprises ribs to which adhesive is applied. In U.S. Pat. No. 4,776,670 a description is given of a holder which is triangular in cross-section and which has deformable side walls. In the U.S. Pat. No. 4,818,069 it is stated that profiles are provided in the surfaces to be cemented. These mechanical solutions, however, do not solve the underlying cause of the problem, namely the shrinkage of the adhesive layer during curing.